Positive Electrode Coating Composition for Stable Ca/Sr Retention
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Solution Overview
Problem
Transition metals like Ni and Mn from positive electrode active materials in secondary batteries can elute during charge and discharge, destabilizing the crystalline structure and affecting battery capacity, particularly in high-energy density batteries, and there is a need to improve the stability of coating layers containing elements like Ca and Sr.
Innovation Solution
A positive electrode active material with a lithium-transition metal composite oxide and a coating layer containing elements like Ti, Ca, and Sr is developed, where the coating layer forms a stable compound with the common element Ti, inhibiting the elution of transition metals and improving the stability of the coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer containing Ca or Sr is formed on the lithium-transition metal composite oxide, then the elution of transition metals is inhibited, but Ca or Sr may be eluted from the coating layer
Solution Approach 1:
The patent applies composite materials by combining multiple metal elements (Ti, Al, Si, Ge, or Sn) in the coating layer to create a synergistic effect. This composite coating structure prevents elution of both transition metals from the lithium-transition metal composite oxide and coating layer metals (Ca/Sr), achieving enhanced stability without element loss.
2Object-affected harmful factors
If the coating layer contains Ca or Sr, then it provides protective function, but stability of the coating layer has not been sufficient
Solution Approach 1:
The patent changes the compositional parameters of the coating layer by incorporating specific metal elements (Ti, Al, Si, Ge, or Sn) in controlled amounts. This compositional modification enhances the chemical stability and structural integrity of the coating layer, preventing both transition metal elution and coating layer degradation.
3Quantity of substance
If high energy density is achieved using lithium-transition metal composite oxide, then battery capacity is improved, but transition metal elution is significantly increased
Solution Approach 1:
The coating layer acts as an intermediary barrier between the lithium-transition metal composite oxide and the electrolyte. This intermediate layer prevents direct contact and chemical reactions that cause transition metal elution, while allowing the high-capacity material to function effectively, thus maintaining battery capacity without the harmful elution effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively inhibits the elution of transition metals and Ca/Sr from the positive electrode active material, enhancing the stability and performance of non-aqueous electrolyte secondary batteries by maintaining battery capacity and charge-discharge cycle characteristics.
Implementation Method 1
the coating layer forms a stable compound with the common element Ti, inhibiting the elution of transition metals and improving the stability of the coating layer
Data Source
AI summary
This positive electrode active material for nonaqueous electrolyte secondary batteries comprises: a lithium transition metal composite oxide which is represented by general formula LixM12−yM2yM3zOwFv (wherein 1≤x≤1.2, 0<y<1, 0.001≤z≤0.1, 0≤v≤0.2, 3.8≤w+v≤4.2, M1 represents one or more elements selected from the group consisting of Ni, Co and Mn, M2 represents one or more elements selected from the group consisting of Ti, Fe, Al, Ge and Si, and M3 represents one or more elements selected from the group consisting of Ca and Sr), while containing M1 and M2; and a coating layer which is formed on at least a part of the surface of the lithium transition metal composite oxide, while containing M2 and M3.